Population dynamics and assessment of Golden Trevally, Gnathonodon speciosus (Forsskål, 1775), in the Southern Arabian Gulf off the United Arab Emirates

The population dynamics of Gnathonodon speciosus from the southern Arabian Gulf off the United Arab Emirates was investigated based on direct and indirect methods to validate the age. The average growth parameters based on the methods were estimated as L_∞=84.52cm TL, K=0.28 and t_o=-0.45years_.  The fitted Von Bertalnaffy’s growth equation for G.speciosus was L_t=84.52*[1–exp-0.28*(t+0.45)]. The estimated growth performance index Ø was 3.30 while the estimated life spans close to 11.0 years. The instantaneous coefficient rates of total mortality Z estimated by length converted catch curve was 1.01yr^-1. Natural mortality M estimated by pauly, Rikhter&Efanov and Hoeing methods were 0.62, 1.02 and 0.41yr^-1 respectively with average 0.68yr^-1 for further analysis. Peaks in spawning occurred during March, April and May. Yield per recruit Y/R and biomass per recruit B/R were estimated as 171.7&520.3g respectively at current F=0.33year^-1 and T_c=1.59 year. Estimates of relative yield per recruit and relative biomass per recruit were E_0.1=0.62, E_0.5=0.35 and E_max=0.74 indicates the stock of G.speciosus is under-exploited.

Keywords: Gnathonodon speciosus, Growth, Mortality, spawning season, yield per recruit